4 Answers
4

You can use Krita. Krita is a free sketching and painting program. It was designed for concept art, illustrations, and texture painting. You can see what features are Krita supports here. Krita is an open source software. It's available on Linux. You can check it out here.

Pinta is like PaintDotNet but is open source and multi platform. It is a simple image editor with a simpler interface than gimp. I think you can run sudo apt-get install pinta. Otherwise there's PPAs on the site or you can build from source.

For posterity, I recommend KolourPaint. It's an MS Paint clone (i.e., as prior to Windows 7) from KDE, but unlike other MS Paint clones (I have tried them all) it is actually as intuitive and quick as the original. Its user interface is a lot less menu-y than Pinta, and it loads far faster than GIMP, Krita, or Inkscape.

It doesn't support layering but for quick and dirty stuff I don't find this to be much of a problem.

Inkscape is a vector drawing package which I find useful for quick drawings and diagrams. It is in the repos and I believe it can easily be installed with sudo apt-get install inkscape (I'm on Debian, but the install command should be the same.